Systems for displaying electronic devices in a store have been devised that supply electrical power to the devices so that a potential buyer can actually pick up and use the electronic device, such as a camcorder or camera, in the store before purchasing it, to select the best model for that particular customer.
One such system is shown in U.S. Pat. No. 6,386,906 B1 to Burke (herein incorporated by reference). This system is configured to support several different electronic devices made by different manufacturers, which require different power cables and jacks, and often require different voltages. To supply the different voltages, the system has several transformers that convert 110 volt AC current to DC current at three voltages, e.g., 4.5, 7, and 8 volts. Each device is connected to a power supply base by a cable that carries the DC current for all three voltages. At the other end of the cable, an appropriate jack is provided connected to the appropriate conductor of DC for the required voltage of the associated electronic device.
Systems of the prior art have the disadvantage that they support only devices that can work with the set of voltages provided by the transformers of the base power supply, and updating the system to other different voltage levels for new devices to be displayed requires modification of the circuitry of the base. There are many camcorders on the market, and they have a wide variety of voltages that are required, some being listed below in Table 1. It is not possible to provide such a wide range of possible voltages using systems of the prior art without substantial modifications.
TABLE 1Panasonic PV-DV53D7.2vPanasonic PV-DV353D6vJVC GR-SXM250V11vCanon ZR60A8.4vSharp VL-NZ5010vSharp WLAH1517vOlympus C-504.8vHP 8506vKodak LS4435vOlympus C-7206.5vFuji 38005vKodak CX42303vOlympus D-3903.4v
Another drawback of the prior art is that the cable carrying power requires a number of wires, because there are three currents at different voltages, making the power cable heavier and more expensive. Also, the length of the cord can result in a substantial drop in voltage relative to the input voltage, due to resistance in the cable, with the output voltage being less than the input voltage, and possibly outside the proper working voltage range for the associated electronic device.